Hewertson et al. in J. Chem. Soc., 1963, 1670 disclose the preparation of 2,4,6-tris(dialkoxyphosphinyl)-1,3,5-triazines from cyanuric chloride and trialkyl phosphites. Also disclosed is the tris(diphenylphosphinyl) derivative which decomposes above 300.degree. C. and hydrolyzes readily to cyanuric acid and diphenylphosphinic acid. The preparation of bis(diphenylphosphinyl)-1,2,4,5-tetrazine is disclosed by Disteldorf et al. in Ann., 1976, 225. The preparation of various dialkyl 2-, 4- and 5-pyrimidylphosphonates is disclosed by Kosolapoff et al. in J. Org. Chem., 26, 1895 (1961).